
SOLUBILITY OF SOIL POTASH IN VARIOUS SALT 

SOLUTIONS 

DONALD KITELEY TRESSLER 



SOLUBILITY OF SOIL POTASH IN VARIOUS 
SALT SOLUTIONS 



BY 

DONALD KITELEY TRESSLER 



A THESIS 

Presented to the Faculty of the Graduate School 

of Cornell University for the Degree of 

Doctor of Philosophy 



RE FEINTED FROM 

Soil Science, Vol. 6, No. 3. September, 1918 



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Reprinted from Soil Science, 
Vol. VI, No. 3, September, 191S 



THE SOLUBILITY OF THE SOIL POTASH IN VARIOUS SALT 

SOLUTIONS 1 

DONALD KITELEY TRESSLER 

Bureau of Fisheries, United Stales Department of Commerce 
Received for publication September 13, 1918 

HISTORICAL 

In this the day of extremely high-priced potash when the supply of potash 
does not keep up with the demand, the question of whether other elements 
can unlock potash from the insoluble minerals of the soil is of vital impor- 
tance. If there are minerals which can liberate soluble potash from some of 
the insoluble minerals of the soil and thus make available for the use of the 
plant the immense stores of mineral potash which the soil contains, they 
should be commended for the use of the farmers. 

The various text-books contain many conflicting statements in regard to 
the power of sodium, calcium and magnesium to replace potassium. It is 
the purpose of this work to clear up this point, if possible. 

The up-to-date publications on soil fertility were examined and it was found 
that the following said that lime replaced some potash in the soil: Aikman, 
Blair, Halligan, Hall, Hart and Tottingham, Ingle, Lincoln and Walton, Van 
Slyke, Vivian, and Voorhees. Briggs andBreazeale, Gaither and Keitt and King 
and Curry and Smith were dubious as to whether any replacement took place. 

The authors who were of the opinion that gypsum replaced potash are listed 
as follows: Snyder, Hilgard, Aikman, Hopkins, Keitt and King, Ingle, Voor- 
hees and Van Slyke. Harter, Curry and Smith and Murray do not seem to 
have much faith in the power of calcium sulfate to set free potash. 

There is more disagreement among the writers in regard to the action of 
common salt than as to the action of the calcium compounds. Aikman, 
Curry and Smith, Snyder, Hall, Storer, Lyon, Fippin and Buckman, and 
Van Slyke credit common salt with the power of replacing potash in soils. 
Hart and Tottingham, Voorhees, Murray, and Roberts are doubtful as to 
the power of salt in this regard. 

The question of the liberation of potash is not a new one. E. Wolff [cited 
by Storer (21)] about 1850 was probably the first to point out the possibility 
that potash might be replaced by the soda of common salt. He grew a field 
of buckwheat, one half of which he manured heavily with common salt while 

1 A thesis submitted to the faculty of the Graduate School of Cornell University, in partial 
fulfillment of the requirements for the degree of Doctor of Philosophy. 

237 



238 



DONALD KITELEY TRESSLER 



the other half was unmanured. On analyzing the ashes of the buckwheat 
straw he found that the portion of the crop that had received the salt con- 
tained less soda but more potash than the other. (The statement that Wolff 
was the first to point out the possibility of the replacement of potash by soda 
in soil, does not infer that Wolff was the first to use common salt as a manure. 
At that time salt was quite a common manure in England and France, but 
its value was somewhat debated. In doing his work Wolff was working on 
the theory of mineral nutrition of plants.) 

• Boussingault in about 1860 showed the effect of lime and gypsum on the 
clover grown on some soils, by analyzing the ash of limed and unlimed clover 
and also plastered and unplastered clover. His results are given in the 
following tables [cited by Halligan (13)]: 

Composition of clover ash 





KILOS PER HECTARE 




Unlimed 


Limed 




First year 


Second year 


First year 


Second year 


Lime 


32.2 
26.7 
11.0 


32.2 

28.6 
7.0 


79.4 
95.6 

24.2 


102.8 


Potash 


97.2 


Phosphoric acid 


22.9 







Composition of clover ash-gypsum tests 






WITHOUT GYPSUM 


WITH GYPSUM 




per cent 

23.6 

1.2 

7.6 

28.5 

1.2 

4.1 

9.7 

3.9 

20.0 


per cent 
35.4 




0.9 




6.7 




29.4 


Oxides of iron and manganese 


1.0 




3.8 




9.0 


Sulfuric acid 


3.4 




10.4 







In the first table it is seen that the percentage of potash in the ash increases 
more than the percentage of lime. It hardly need be pointed out that the 
increase of the percentage of potash in the ash might be due to other factors 
than the liberation or replacement of potash by the lime or the gypsum. 

Considerable work was accomplished on the solubility of the soil potash in 
various salt solutions about the year 1860. Dietrich (7) performed some ex- 
periments concerning the solubility of soil constituents in various solutions. 
He found that the alkali metals of the soil were much more soluble in water 
containing carbon dioxide than in pure water. He found that calcium car- 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 239 

bonate dissolved in carbonic acid solutions dissolved about the same amount 
of total alkalis as did carbonic acid of equal strength. In later work (8) 
Dietrich found that N/20 solutions of sodium chloride, calcium chloride and 
lime dissolved much more potassium from soils than did pure water. He 
found that sodium nitrate and sodium carbonate solutions did not dissolve 
potash. He concludes that by the manuring of a field with common salt, 
important amounts of potash are set free. 

Eichhorn (9) in 1858 tried the solvent powers of sodium chloride solutions 
and found that somewhat more potash was dissolved in these solutions than 
in water. Beyer (2) tried the action of various solutions on feldspars and 
measured the amount of potash dissolved. Calcium sulfate was not found to 
have any marked effect on the potash. Sodium chloride solutions and also 
the nitrate solutions were found to exert a powerful solvent effect on the 
potash. Sodium nitrate was less active than the chloride. 

Harry Snyder (19) in 1893 came to the following conclusion as a result of his 
experiments on the soils of Minnesota. 

The indirect action of land plaster (gypsum) on these soils (western and central prairie 
soils — black soils resting on yellow clay) in liberating plant-food, particularly potash and 
phosphoric acid, is unusually marked. Experiments conducted in this laboratory have shown 
that small amounts of gypsum are quite active in rendering potash, phosphoric acid and even 
nitrogen soluble in the soil water. It is not the land plaster itself that furnishes the food, 
but it is the power that it possesses in making mineral matters available that are already in 
the soil. Land plaster acts more as a stimulant and not as a direct fertilizer, and if not used 
to excess it will be a profitable fertilizer to use on these soils, especially to bring in grass and 
clover. 

The writer has been unable to find any further reference to the laboratory 
work which Snyder says was performed at the Minnesota Agricultural 
Experiment Station. 

The Rothamsted Experiment Station has been carrying on experiments 
concerning the manuring of mangels with soda since 1876. The results (12) 
seem to indicate that manuring with common salt increases somewhat the 
percentage of potash in the mangels, but it also increases greatly the percentage 
of soda in the mangels. The yield of the crop was greatly increased by the 
addition of soda. The total amount of potash in the crop of mangels was in 
most cases increased by about one-half. Hall, in discussing these experi- 
ments, states that this increase is due to the attack of the soda salt upon the 
insoluble potash of the soil. The conclusion which Hall (11) draws is quoted 
as follows: 

Since soluble alkaline salts are beneficial to the mangel crop either as direct foods or as 
economizers of potash, a dressing of salt should always be included among the manures for 
the mangel crop. 

Wheeler (23) in drawing conclusions from the experiments (24, 25, 26, 27, 
28, 29) with sodium salts at the Rhode Island Experiment Station, says: 



240 DONALD KITELEY TRESSLER 

As a result it appeared that possibly unable to wholly replace potassium in any one func- 
tion, or at least in all of its functions, in connection with the growth of certain plants, sodium 
may and often does perform some part of one or more of the important functions of potassium 
and thus increase the amount of dry matter which the plant can produce. 

The experiments referred to have been over a period of more than twenty 
years. Wheeler thinks that the most important function of the sodium salts 
is not, therefore, the action on the potash-bearing minerals of the soil, but 
rather as a direct plant nutrient. 

Curry, Smith and others (6) of the New Hampshire Agricultural Experi- 
ment Station have carried out a large number of experiments relative to the 
solubility of potash in various salt solutions. They percolated solutions of 
lime, sodium chloride, sodium carbonate, sodium nitrate, acid phosphate and 
other salts through columns of soil. They stirred feldspar with these various 
solutions and also stirred a mixture of feldspar and clay with the solutions. 
They tried the solubility of feldspar in solutions of lime, gypsum, sodium ni- 
trate, ammonium sulfate, sodium carbonate and disodium phosphate. They 
found that all of these salts increased the solubility of the potash contained 
in the feldspar, lime having the greatest solvent action. However, when the 
feldspar was mixed with clay the lime solution had even less solvent action 
than pure water. They observed that when solutions of sodium nitrate, so- 
dium chloride, sodium carbonate and acid phosphate are percolated through 
columns of soil more potash is made soluble than when water is percolated. 
They conclude that calcium carbonate and lime have practically no effect on 
the solubility of the soil potassium, and that the calcium sulfate makes but 
small amounts of potassium soluble. However, they say that the effect of 
sodium chloride, sodium nitrate, sodium carbonate and acid phosphate is to 
greatly increase the solubility of the soil potassium. The reaction, they be- 
lieve, between these salts and the soil is chemical. 

Soderbaum (20), working on plot experiments in 1911, however, concluded 
that the beneficial results obtained from the use of common salt as a fertilizer 
were due to the effect of the chlorine which was introduced and not to the 
sodium. 

Bradley (3) of the Oregon State Agricultural College worked on the effect 
of lime and gypsum upon the soils of Oregon. He mixteti the soils with either 
lime or gypsum in large glass percolators and allowed the soils to stand at 
the optimum moisture content for six weeks. He analyzed the solutions ob- 
tained by leaching these soils. He found that both lime and gypsum set 
potash free. The gypsum, however, was more active in this regard than the 
lime. He also tried shaking the soils with solutions of lime and gypsum. 
In this case he found that the lime decreased the amount of potash going into 
solution, whereas the gypsum increased it greatly. He concludes that gypsum 
sets free potash in the soils of the Willamette Valley. 

Gaither, of the Ohio Agricultural Experiment Station (10) working with 
plot tests determined the solubility of the various elements in N/5 nitric acid. 



SOLUBILITY OF SOIL POTASH EN SALT SOLUTIONS 241 

He concludes that lime breaks up certain silicates in the soil and renders them 
more soluble in N/5 nitric acid but does not act upon the insoluble potassium 
compounds in the soil to such an extent that N/5 nitric acid can be used as a 
measure of such potash. The addition of caustic lime has the effect of di- 
minishing the amount of potash assimilated by wheat grown on such soil. 
The theory that lime added to the soil increases the amount of available potash 
in the soil is either erroneous or requires more positive proof than has hereto- 
fore been obtained, before it can be accepted. 

Andre (1) in 1912 worked on the replacement of potash in certain feldspathic 
rocks by the addition of sea salt or of sodium nitrate. He found that the 
potash of microcline was quite noticeably dissolved by solutions of sea salt 
or sodium nitrate; the amount of potash going into solution being almost the 
same in both cases. He concludes that the replacement explains the favor- 
able action of salt when used as a fertilizer. He thinks that sodium nitrate 
is valuable as a fertilizer not only for the nitrogen that it furnishes, but also 
because the sodium added to the soil sets free a certain amount of potash. 

Iakushkin (16) found that the addition of sodium chloride as a fertilizer 
increased the yield of Japanese millet 52 per cent. The beneficial effect of 
sodium was observed in a complete normal nutrient solution, thus indicating 
that the action of sodium is not due to the replacement of potash. 

Hartwell and Wessels have published data (14) concerning the experiments 
at the Rhode Island Agricultural Experiment Station of a more recent date 
than that of Wheeler previously referred to. They observe that soda can 
partially replace potassium as a fertilizer for mangels and onions. If liberal 
applications of sodium manures were applied, an- equally large yield of onions 
and mangels were obtained even when the amount of potash manures had 
been reduced one-third. However, when the potash ration was reduced one- 
half, in some cases the crop yield was reduced somewhat. 

Briggs and Breazeale (4) of the Bureau of Plant Industry, have recently 
finished some work which seems to prove the opposite of much of the work 
which has been cited. Their article in the Journal of Agricultural Research 
excited considerable comment and a number of persons, including the writer, 
have attempted to duplicate the results which they reported. They deter- 
mined the solubility of pegmatite and orthoclase in calcium hydroxide and 
calcium sulfate solutions of various concentrations. The calcium hydrate 
solutions did not modify the solubility of the potassium in either pegmatite 
or orthoclase. Gypsum solutions depressed the solubility of the potassium 
in orthoclase, the quantity of potash in the solution decreasing progressively 
as the concentration of the calcium sulfate solution increased. 

Similar tests were made upon a virgin soil of a granitic type. The solubility 
of the potash was not measurably different in distilled water and in solutions 
of calcium sulfate or calcium hydroxide. In the case of a soil of similar nature, 
which had been under cultivation for some time, which was somewhat more 



242 DONALD KITELEY TRESSLER 

granular and less weathered than the virgin soil, the addition of calcium sul- 
fate decreased the solubility of the potash. They conclude: 

The experiments indicate that the availability to plants of the potash in soils derived from 
orthoclase-bearing rocks is not increased by the addition of lime or gypsum. In some in- 
stances a marked depression of the solubility of the potash in the presence of gypsum was 
noted. 

In some recently published work (17) concerning some lysimeter experi- 
ments, Lyon and Bizzell have shown that the application of lime to soils did 
not result in an increase in the quantity of potash contained in the drainage 
water, nor in any increase in the amount of the potassium contained in the 
crops. 

From the foregoing review of the literature, it is seen that about the year 
1860 it was generally accepted that calcium and sodium salts did liberate potash 
from the soil. Although this was accepted as a fact, insufficient proof was 
given. Recently Wheeler has suggested that perhaps the plant did not de- 
rive its benefit from the potash set free when salt was applied to the soil, but 
from the element itself. Within the last decade a number of experimenters 
have again attacked the problem of liberation of potash. Different men have 
obtained different results. There is not the agreement of results from which 
the truth can be deduced. The writer wishes to point out that the various 
workers have used different types of soil and that it is but natural that they 
should get different results. No general statements can be made from the 
experimental work performed with one type of soil. Experimenters should 
use many types of soil from, many localities and then draw their conclusions 
for the types of soil used in their experiments. 

EXPERIMENTAL 

In this work no effort was made to determine the nature of the phenomenon 
of the liberation of potash from the soil minerals by the salt solutions. The 
writer determined the amount of potash that dissolved in salt solutions. An 
attempt was made to determine the effect of the concentration of the solution. 
Various types of soils were studied with particular reference to the effect of 
solutions of calcium sulfate upon the potash which they contain. Besides 
studying the effect of the various calcium salts upon the soil potash, the effects 
of various sodium salts were studied. 

The solubility of the soil potash in carbonic acid and in calcium bicarbonate 
was compared, in order to throw some light upon the action of lime or calcium 
carbonate upon the potash contained in the soil minerals. 

Soils which had been manured with gypsum for years were compared in 
regard to the solubility of the soil potash in gypsum solutions with check soils, 
which had never been treated with gypsum. It was hoped that this might 
give some information on the residual effect of gypsum as a fertilizer. 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 243 

THE METHOD 

The method used in the experiments was practically the same in all cases. 
It consisted in merely allowing the soil to remain in contact with the various 
salt solutions until the systems came to equilibrium. One hundred and twenty 
five grams of dry soil, or its equivalent in moist soil, was placed in a liter of 
water contained in a 2-liter bottle. Various amounts of salts were added to 
the solutions and they were allowed to stand for 3 weeks. During this period 
they were shaken once or twice a day. In order to determine whether the 
soil potash was more or less soluble in the salt solutions, blank determinations 
were run in all cases. In other words, no salts were added to some of the 
soil samples but the soil was merely allowed to stand in contact with the 
water under the identical conditions. 

In case this procedure was altered in any way, it is noted in connection 
with the results. 

It was determined by experiment that at least 2 weeks are required for the 
soil to come into equilibrium with the solution. At the end of a week the 
amount of potash found in one of the solutions was 2.1 parts per million. At 
the end of 2 weeks the same solution contained 3.2 parts of potash per million 
and at the end of 3 weeks the amount had not changed perceptibly. In order 
to be reasonably sure that the soil was in equilibrium or nearly so with the 
solution, the solutions were allowed to remain in contact with the soil for 3 
weeks. At the end of that time the solutions were decanted off from the soil 
and were filtered through a Pasteur-Chamberland porcelain filter. 

Potash was determined in the solutions. The method used was a modified 
Cameron and Failyer method. This method was first described by the above 
men in the Journal of the American Chemical Society (5). To an aliquot of 
the solution some ammonium oxalate solution and a couple drops of a 10 per 
cent ammonium carbonate solution were added. The amount of ammonium 
oxalate added depended upon the amount of calcium in the solution. If no 
calcium salt was added only three or four drops of a saturated solution of 
ammonium oxalate was added. The solution was then heated to boiling 
and boiled for a minute and then filtered. The filtrate was collected in an 
evaporating dish and the solution evaporated to dryness on a water bath. 
Enough dilute sulfuric acid was then added to moisten the salts and the dish 
was then heated at a dull red heat until the ammonia was completely driven 
off. 

The salts were then taken up in a little water, a drop of pure concentrated 
hydrochloric acid was added, and then sufficient 0.25 per cent chloroplatinic 
acid to react with all the sodium and potassium salts present, after which the 
solution was evaporated to a paste on a water bath. The paste was then 
taken up in alcohol. Ninety-five per cent alcohol was used, for the potassium 
chloroplatinate is less soluble in alcohol of that strength than it is in 80 per 
cent alcohol. The solution was then filtered through asbestos into a Gooch 

SOIL SCIENCE, VOL. VI, NO. 3 



244 DONALD KITELEY TRESSLER 

crucible. The potassium chloroplatinate was well washed with alcohol. 
When no large amount of sodium was present 100 cc. of alcohol were used. 
But when sodium salts were added to the solution it was found necessary to 
wash the chloroplatinate with 150 cc. of alcohol in order to dissolve all of the 
sodium chloroplatinate. After drying the crucible in an oven at 100° for 
a half-hour, the potassium chloroplatinate was dissolved in about 50 cc. of 
hot water and a drop of concentrated hydrochloric acid was added. After 
cooling, a solution of potassium iodide containing at least ten times more than 
enough potassium iodide to react with the chloroplatinate was added and the 
solution allowed to stand over night. During this time a rose color developed 
in the solution and the next morning the color was compared in a colorimeter 
with a standard solution containing a known amount of potassium chloro- 
platinate prepared in a similar manner. The most trouble was experienced 
in obtaining checks when sodium salts were present in large quantity. 

When no sodium had been added to the solution no trouble was found in get- 
ting the determinations to check within 0.5 part per million. When large 
amounts of sodium were present checks were usually within one part per 
million. 

DESCRIPTION OF SOILS 

The soil called Dunkirk silt loam which was used in many of the experiments 
is a light brown silt loam. It belongs to the " Glacial lake and river terrace 
province." It is underlain by a slightly heavier subsoil of a brown color. It 
is of a sedimentary origin and represents the wash from the higher slopes 
deposited in quiet glacial lake waters. It is a good soil for general crops. 
That used in the experiments contained 4.7 per cent of organic matter (de- 
termined as loss on ignition) and 1.9 per cent of potash. It was slightly acid 
to litmus paper. It was obtained near Ithaca, New York. 

The soil called Whiteland clay subsoil was obtained in the town of Corvallis, 
Oregon. It belongs to the second bench Willamette type. It is of sedimen- 
tary origin and was laid down by the Willamette River. Whiteland is a poorly 
drained soil of mottled gray and brown color. It is underlain by a heavy 
gray clay and this is the soil used in the experiments. It contained 6.2 per 
cent of organic matter (determined as loss on ignition) and 1.94 per cent of 
potash. It reacted neutral to litmus. This is a very poor soil for all crops. 

The Yamhill silt loam was obtained from near Corvallis, Oregon, and is an 
alluvial soil laid down by the Willamette River. It belongs to the first bench 
soils of the Willamette series. It is a brown loam soil with a brown subsoil 
of finer texture than the surface soil. It reacted neutral to litmus. The 
sample analyzed contained 1.5 per cent of potash and lost 4.8 per cent on 
ignition. It is a very fertile soil. 

The Porters sandy loam belongs to the "Appalachian soil province" and 
is of residual origin. The sample used in these experiments was obtained 
from North Carolina. It is of igneous rock origin, occupies mountainous land, 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 245 

and is dark gray in color. The sample used contained many small glistening 
scales of mica. It contained 10.2 per cent of organic matter; its potash con- 
tent was 1.2 per cent, and its reaction towards litmus was neutral. The sam- 
ple was from a fertile field. Wheat, corn, oats, rye and potatoes are the prin- 
cipal crops grown on it. 

The Durham sandy loam is a soil belonging to the Piedmont soil province. 
The sample used in the experiments was obtained from North Carolina. The 
soil is a light sandy loam underlain by a pale yellow sand. The type is de- 
rived from a light-colored granite. Owing to a lack of organic matters the 
soil dries out quickly. The sample taken, however, contained more than the 
average amount of organic matter for this type — 8.7 per cent. Its potash 
content was 0.4 per cent. It reacted slightly acid to litmus. The soil is not 
especially fertile. 

The Genessee humus loam is a recently formed alluvial soil, formed from 
reworked glacial till. The sample used was obtained near Ithaca, New York. 
It was mottled black and brown and although it contained considerable coarse 
sand it also contained a relatively high proportion of clay. It was of only 
average fertility, although it contained 15.7 per cent of organic matter. Its 
reaction towards litmus was neutral. 

The Merrimac fine sandy loam was obtained from the experimental plots 
of the Massachusetts Experiment Station, Amherst, Massachusetts. The 
surface soil consists of a light-brown fine sandy loam. This type occurs as 
narrow terraces along rivers and represents glacial flood-plain deposits. The 
soil is a very fertile one, and brings a high price per acre, onions and tobacco 
doing particularly well on it. It contains 2.2 per cent of organic matter and 
1.7 per cent of potash. 

The chief idea in choosing the above soils was to get a variety of soils of 
different types and from various sections of the United States. General de- 
ductions cannot be drawn by merely experimenting with one type of soil from 
only one locality. 

EXPERIMENTS CONCERNING THE SOLUBILITY OF THE SOIL POTASH IN ACID 

PHOSPHATE SOLUTIONS 

Curry and Smith (6) of the New Hampshire Agricultural Experiment 
Station, experimented with an acid phosphate free from potash and deter- 
mined the solubility of the soil potash in a very dilute solution of this phos- 
phate. They percolated this dilute solution through a column of soil and 
found that there was a considerable increase in the amount of potash in the 
percolate. They concluded that the effect of commercial acid phosphate when 
applied as a fertilizer is to greatly increase the solubility of the soil potassium. 
They however did not attribute the action of the acid phosphate to any one 
compound contained in the acid phosphate. 



246 



DONALD KITELEY TRESSLER 



Commercial acid phosphate consists chiefly of a mixture of monocalcium 
phosphate, dicalcium phosphate, tricalcium phosphate and calcium sulfate. 
Any liberation of potash would be due to one or all of these compounds. Dun- 
kirk silt loam was shaken with saturated solutions of these salts and the amount 
of potash in the solutions noted. The results are given in table 1. 

In this and all subsequent tables the amounts of potash are expressed as 
K 2 in parts per million of solution. 

It is seen from the table that the only substance which increases the solu- 
bility of the potash to any appreciable extent is the calcium sulfate. Yet in 
this same paper in which Curry and Smith state that acid phosphate is so 
active in liberating potash from the soil, they say that "A limited number 
of experiments with calcium sulfate indicate that small amounts of potassium 
are made soluble." 

The results of the above experiments seem to indicate that tricalcium phos- 
phate has little or no action on the soil potash. The same is true in regard 

TABLE 1 

Potash liberated in Dunkirk silt loam 



Merely distilled water 

Calcium sulfate 

Tricalcium phosphate 

Dicalcium phosphate 

Monocalcium phosphate 

A and B are duplicate experiments 





CONCENTRATION OF POTASH IN 
SOLUTION IN PARTS PER MILLION 




A 


B 




3.8 
11.8 
3.2 
3.4 
1.5 


3.4 




11.8 




3.0 




4.0 




2.0 



to the dicalcium phosphate while the monocalcium phosphate seems to have 
a negative effect. It seems therefore that if acid phosphate has any beneficial 
effect on soil in making potash soluble, this effect is due to the calcium sulfate 
which it contains. 

In order to learn whether the above conclusion held for other soils, two 
other soils were tried with the same salt solutions. In this experiment, a 
Whiteland clay subsoil and a Yamhill soil were tried. The results were simi- 
lar except in the case of the calcium sulfate solution. They are listed in 
table 2. 

In these other soils the calcium sulfate does not seem to have any action 
in making potash soluble. In one case, the dicalcium phosphate and tricalcium 
phosphate seem to keep the potash from going into solution. In the case of 
the Yamhill soil which is coarser in texture than the other soils, these phosphates 
have little action on the potash. In all three soils the monocalcium phos- 
phate apparently hinders the solution of the potash. We must conclude, 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 



247 



therefore, that only on certain types of soil does calcium sulfate have any ac- 
tion. And since calcium sulfate is the active principle of commercial acid 
phosphate, the same holds true of acid phosphate. 

TABLE 2 
Potash liberated in Whiteland clay subsoil and Yamhill soil 



Distilled water only , 

Calcium sulfate 

Tricalcium phosphate . . . 
Monocalcium phosphate 



CONCENTRATION OF POTASH IN 
SOLUTION IN PARTS PER MILLION 



Whiteland 
subsoil 



3.2 
3.2 
1.8 
0.9 



Yamhill soil 



3.0 
3.2 
3.2 
0.9 



EXPERIMENTS CONCERNING THE SOLUBILITY OF THE SOIL POTASH IN SOLUTIONS 

OF CALCIUM SULFATE 

The above-outlined experiments indicated that all soils were not uniformly 
affected by calcium sulfate solutions. Seven soils, from four different states, 
varying widely in characteristics and properties, were taken and tested as to 
their solubility in saturated calcium sulfate solutions. The results are listed 
in table 3. 

TABLE 3 
Results showing solubility of soil potash in solutions of calcium sulfate 



Whiteland clay subsoil. . . 

Dunkirk silt loam 

Yamhill silt loam 

Genessee humus loam. . . . 
Merrimac fine sandy loam 

Durham sandy loam 

Porters sandy loam 





SOLUTION 


Distilled water 


Calcium sul- 
fate solution 


p. p. m 




p. p. m. 


3.2 




3.2 


3.5 




11.8 


3.0 




3.2 


5.5 




7.4 


1.0 




1.3 


4.8 




5.7 


3.5 




3.7 



Aside from the Dunkirk silt loam, Durham sandy loam and Genessee 
humus loam are the only soils that showed any marked effect of the action of 
the gypsum solution. 

Because of the extraordinary action of solutions of calcium sulfate upon the 
Dunkirk silt loam the writer experimented further with this soil. Five 
hundred grams of it were taken and separated mechanically into clay, silt 
and sand. The sand was considered as being composed of those particles 



248 



DONALD KITELEY TRESSLER 



above 0.05 mm. in diameter; the silt, those particles between 0.05 and 0.005 
mm. in diameter; and the clay all particles of smaller diameter than 0.005 
mm. The soil was shaken for 12 hours to deflocculate it. The clay and silt 
were then separated from the sands by simple subsidence and decantation. 
The silt was separated from the clay by whirling the soil in the water in tubes 
in a centrifuge. After the separation the soil separates were dried. Thirty 
grams of the three separates were treated with 500 cc. of an approximately 
saturated calcium sulfate solution for 3 weeks. Like amounts of the separates 
were treated with a like amount of distilled water. At the end of 3 weeks the 
soil solutions were filtered and the potash determined in the solutions. The 
results are presented in table 4. 

The sand contained but 2.2 per cent of organic matter while the silt con- 
tained practically the same amount as did the entire soil, 4.6 per cent. There 
was not enough of the clay left over to determine the organic matter (as loss 
on ignition) but the clay must have been high in organic matter, as that must 
have contained the organic matter which was missing from the sand. Some 
organic matter was probably dissolved and this would be contained in the 
clay. 

TABLE 4 

Results showing the- solubility in calcium sulfate of potash in Dunkirk silt loam 





SEPARATE 


SOLUTION 


Entire soil 


Sand 


Silt 


Clay 


Distilled water 


4.7 
8.1 


3.2 
4.7 


5.9 
8.8 


17.9 




25.1 







It is noteworthy that although some liberation of potash occurs in all three 
separates, the greater portion of the liberation occurs in the clay. As the 
particles become smaller the solubility of the potash increases and the amount 
made soluble by the gypsum increases. 

In the above experiment the amount of potash dissolved by water alone 
was higher than in the previous experiments. This experiment was carried 
out in hot weather, whereas the previous experiments were conducted during 
cold weather. This was one of the factors which caused the increased solu- 
bility of the soil in distilled water. 

Way (22) in 1850 found that soil absorbed potash. Solutions of potassium 
nitrate were filtered through columns of soil and the percolate contained no 
potash. In the above experiments the soil was treated in a fine suspension in 
solution and was well shaken so that the clay, which possesses most of the 
absorbing power of the soil, was entirely in suspension. It is conceivable that 
when a solution of calcium sulfate slowly percolates through the soil, as is the 
case when gypsum is added to the soil as an amendment, the gypsum may lib- 
erate the potash and have it remain in the soil. In fact, it would be sur- 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 



249 



prising if we would have any very large amount of potash in the drainage water 
from any lysimeter containing a heavy clay soil. The fact, then, that the 
analysis of water from lysimeter tanks does not show an increased amount of 
potash in solution due to the addition of gypsum to the soil does not necessarily 
prove that there is no liberation of potash by the gypsum. Experiments such 
as the above, in the writer's opinion, would be more positive proof that potash 
is made more soluble. For if the potash were liberated there would be little 
chance for the clay to absorb it and remove it from solution. 

Insufficient work has been done to make it possible to state definitely in just 
what soils a marked replacement of potash could be expected. The Porters 
sandy loam was of average potash content (1.2 per cent) and even contained 
a large number of flakes of mica, yet there was practically no replacement of 
potash. Curry and Smith and others have found that gypsum solutions will 
dissolve some potash from the natural potash-bearing rocks, but the amount 
is small. The writer is of the opinion that the action on the clay is much more 
important. It seems probable that there will be an increase in the solubility 
of the potash due to calcium sulfate in fertile clays and loams containing a 
considerable amount of potash. 

TABLE 5 
Results showing liberation of potash from Dunkirk sill loam by different concentrations of calcium 

sulfate 





CONCENTRATION OF SOLUTIONS 




No calcium sul- 
fate 


1.36 gm. per 
liter 


0.68 gm. per 
liter 


0.34 gm. per 
liter 


0.17 gm. per 
liter 


A 
B 


p. p. m. 

5.1 

5.2 


p. p. m. 

8.9 
8.9 


p. p. m. 

8.9 

8.8 


p. p. m. 
8.4 
8.1 


p. p. m. 

7.0 
6.8 



A and B are duplicate experiments. 

In order to determine how much calcium sulfate must be present in solution 
in order to have any appreciable liberation of potash from Dunkirk silt loam, 
solutions of different concentrations were used and the amount of potash 
dissolved measured as before. The results are given in table 5. 

Figure 1 shows graphically the amount of potash set free at any concentra- 
tion of solution. It should be noted that 1.36 gm. of calcium sulfate is a 
third more than will dissolve in a liter of water. This partially explains why 
half as much of the salt set free as much potash. 

The fact that 0.170 gm. of calcium sulfate in a liter of solution, or, in other 
words, 170 parts per million, made 1.75 parts per million of potash soluble is 
surprising. If 150 pounds of calcium sulfate were applied to an acre of soil 
and if the gypsum all dissolved in the moisture in the first foot, at a 20 per 
cent moisture content the concentration of the calcium sulfate would be ap- 
proximately 170 parts per million. This may account for the fact that, on 



250 



DONALD KITELEY TRESSLER 



some soils, merely small applications of calcium sulfate have a remarkable 
action in increasing the crop yields. When large amounts of gypsum are ap- 
plied to soils the deleterious physical effect of the addition seems to overcome 
the benefits derived from its use. 

Through the kindness of Dr. F. W. Morse, acting-director of the Massa- 
chusetts Agricultural Experiment Station, samples of soil were obtained from 
the plaster and check experimental plots of that station. The soil is of the 
Merrimac fine sandy loam type, and is considered a very fertile soil. Soil 
from plot 11 and plot 12, which is the check plot, was obtained. Plot 11 has 




?io 



r 100 ZOO 300 300 50*j 500 1 TOff BDT5 5075 lOOO — ITOO — 1200 
Concentration of calcium sulphate solution in parts per million 

Fig. 1. Curve Showing Effect of Concentration of Calcium Sulfate Solution on 
the Solubility of Soil Potash 



been dressed annually with 800 pounds of "plaster" since 1890. These soils 
were tested with calcium sulfate solution in the same manner as the other soils, 
except that the soils remained in contact with the solutions for 5 days only. 
However, they were shaken more frequently. The results of these experi- 
ments are shown below. 

As in the following experiments, the calcium sulfate solution used was a 
saturated solution. 

No very definite facts can be deduced from the results of the above experi- 
ment, but it seems as if the potash in a soil which has been treated with gyp- 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 



251 



son. 


POTASH DISSOLVING IN WATER 


POTASH DISSOLVING IN GYPSUM 
SOLUTION 




A 


B 


A 


B 


Plot 1 1 (plastered) 


p. p. m. 
1.2 
1.0 


p. p. m. 

1.3 
1.0 


p. p. m. 

1.5 
1.2 


p. p. m. 
1.4 


Plot 12 (check) ' 


1.5 







A and B are duplicate experiments. 

sum for a large number of years was slightly more soluble than in the untreated 
soil. This statement requires more conclusive evidence than the above, how- 
ever, before it can be considered as a fact. 



EXPERIMENTS CONCERNING THE SOLUBILITY OF THE SOIL POTASH LN SOLUTIONS 

OF CALCIUM CARBONATE 

Inasmuch as calcium oxide and calcium carbonate are annually added as 
amendments to the soils of the United States in large quantities, it is impor- 
tant that we know whether or not calcium-carbonate solutions have any simi- 
lar action on the soil potash. Calcium-carbonate solutions alone were tried 
(calcium carbonate mixed with soil and distilled water) but because of the 
very slight solubility of the carbonate the results were negative. They are 
listed below: 



Whiteland clay subsoil . 
Yamhill silt loam , 





POTASH DIS- 


POTASH DISSOLV- 


SOLVING IN CAL- 


ING DM WATER 


CIUM CARBONATE 




SOLUTION 


p. p. m. 


p. p. m. 


3.2 


2.4 


3.0 


3.0 



In each case, 2 gm. of calcium carbonate were added to a liter of water. In 
the case of the Whiteland clay subsoil, the presence of the calcium carbonate 
seemed to depress the amount of potash going into solution. The results of 
the analyses checked closely, but it is possible that they are in error. At any 
rate, there could be no increased solubility of the potash. 

Inasmuch as the. amount of calcium carbonate going into solution in a soil 
water is controlled almost entirely by the carbon dioxide which the water 
contains dissolved in it, it seemed logical to try the solvent action of calcium 
bicarbonate on soil, or in other words, a solution of calcium carbonate in car- 
bon dioxide and water. In these experiments 125 gm. of Dunkirk silt loam 
were taken. Two grams of calcium carbonate and a liter of water were added 
to this soil. The whole was shaken up and kept saturated with carbon diox- 
ide for 5 days, after which the bottles were stoppered up and allowed to stand, 
with the exception of shaking up once a day for 3 weeks. At the end of this 



252 



DONALD KITELEY TRESSLER 



time the solutions were analyzed for potash, as were the other solutions. The 
results of these analyses are given in table 6. 

For purposes of comparison the check determinations with water and with 
water saturated with carbon dioxide are given in the table. In the case of 
Dunkirk silt loam N/50 calcium bicarbonate caused an average increase in 
solubility of 1.55 parts of potash per million. In cases where a ton or more 
of lime is added to the acre there may be an appreciable amount of calcium 
carbonate dissolved in the soil water. In such cases some potash may be af- 
fected by the calcium bicarbonate. 

TABLE 6 

Results showing amounts of potash liberated from Dunkirk silt loam by calcium carbonate 

solutions 





SOLUTION 




Distilled water 


Water saturated with 
carbon dioxide 


Calcium bicarbonate 


A 
B 


p. p. m. 
5.3 
5.2 


p. p. tn. 
8.4 
8.7 


p. p. m. 

9.6 

10.8 


Average 


5.25 


8.55 


10.1 







A and B are duplicate experiments on the same soil. 



EXPERIMENTS ON THE SOLUBILITY OF SOIL POTASH IN SOLUTIONS OF VARIOUS 

SODIUM SALTS 



In studying the action of solutions of sodium salts on soils, sodium nitrate, 
sodium carbonate and sodium chloride were first tried. Table 7 shows the 
effect of these solutions on Whiteland clay subsoil and Yamhill silt loam. 

In the experiment 1.7 gm. of sodium nitrate, 1.169 gm. of sodium chloride 
and 1.06 gm. of sodium carbonate were taken. The amounts mentioned were 
enough to give one-fiftieth of an atomic weight of sodium in grams in a liter 
of solution. These figures certainly show that the soil potash is much more 
soluble in solutions of these salts than in water. The reason why sodium ni- 
trate should be less active, in this regard, than sodium chloride or sodium 
carbonate is not clear. 

In order to ascertain whether or not other soils were affected similarly by 
sodium salt solutions, some other soils were tested out in the same fashion. 
For purposes of comparison, the above-reported results are included in table 
8. The amount of salt added was the same in both cases. 

The potash in all soils is dissolved to a greater or lesser extent by common 
salt solutions. The amount going into solution is much greater in the case of 
the sodium salt solutions than in the case of the calcium sulfate solution or 
of calcium carbonate solutions. It is noteworthy, that, of the soils listed in 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 



253 



TABLE 7 
Results showing the effect of various sodium salts on soil potash 





POTASH DISSOLVED BY THE SOLUTION 


SOIL 


Distilled water 


Sodium nitrate 


Sodium chloride 


Sodium car- 
bonate 




p. p. m. 
3.2 
3.0 


p. p. m. 
4.9 
8.6 


P. p. m. 

13.3 
22.6 


p. p. m. 
14.3 




22.9 







TABLE 



Results showing the effect of sodium chloride on the potash in different soils 



Whiteland clay subsoil 

Yamhill silt loam 

Genessee humus loam. 
Durham sandy loam . . 
Porters sandy loam . . . 



POTASH DISSOLVED BY THE 


SOLUTION 


Distilled water 


Sodium chloride 
solution n/50 


p. p. m. 


p. p. m. 


3.2 


13.3 


3.0 


22.6 


5.5 


13.0 


4.8 


14.8 


3.5 


14.6 



TABLE 9 

Results showing the effect of the concentration of the sodium chloride solution on the solubility 

of potash in Yamhill silt loam 



CONCENTRATION OF THE SODIUM CHLORIDE SOLUTION 


POTASH DISSOLVED , 


grams per liter 


p. p. m. 




0.0000 


1.8 




0.0730 


1.9 




0.1460 


4.1 




0.2923 


12.5 




0.5840 


15.2 




1.1690 


22.6 





table 8, the Yamhill silt loam is the most fertile, and that it is also most af- 
fected by the sodium chloride solution. 

In order to determine the. effect of the concentration of the salt solution, 
the amount of potash going into solution was determined in solutions of sodium 
chloride of various concentrations. In this experiment a different sample of 
Yamhill silt loam was used. The results are listed in table 9. 

Figure 2 shows the results graphically. It will be noted that the increased 
solubility of the potash does not amount to much until the concentration of 
the salt solution reaches about 290 parts per million. At lower concentra- 
tions the increased solubility of the potash is hardly noticeable. This may 



254 



DONALD KITELEY TRESSLER 



account for its successful use on beets, whereas it is harmful to a number of 
other crops. Beets and mangolds need a large amount of potash. They 
seem to require it in the photosynthesis of sugar. According to Shaw (18) 
beets are not harmed even when the amount of sodiun chloride in the first 
four feet of an acre rises to 10,000 pounds. Hilgard (15) lists the common 
crops grown on alkali soils, and sugar beets stand third in order of their re- 
sistance to sodium chloride, the only crops surpassing it in this respect being 



24 

o 
822 


























































a 
a 

a 

ft 20 






























O 

a 
0I8 






























I 16 


























































p 

09 

09 
►1 

3.10 


























































O 

e 






























6 






























4 






























2 






























































« 1 

Concer. 


UO 2U 

t ratio 


30U 
n of t 


,/ 400 
be sod 


50C 
ium oil 


, 60C 

Ion <ie 


solut 


80 
ion is 


90 
parts 


100 

per 11 


11 

dllion 


00 12C 








Fig. 2. Curve Showing the Effect of the Concentration of the Sodium Chloride 
Solution on the Solubility of Soil Potash 



salt grass and modiola. Hall (12) advises the use of sodium chloride as a 
manure for beets, and in England it is a common practice to include sodium 
chloride in the fertilizers for beets. It may be that the beet, not being harmed 
by the increased concentration of salt in the soil solution, derives benefit 
from the potash made soluble by the interaction of the salt with the soil. 
Such is within the realm of reason, for the concentration of sodium chloride, 
in the soil solution would only have to rise to about 300 parts per million 
in order to make considerable potash soluble. 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 255 

SUMMARY 

Certain soils were tried as to their solubility in solutions of the various com- 
ponents of commercial acid phosphate. It was observed that gypsum did 
exert a solvent action on the potash compounds of the soil. The solubility 
of the potash in various soils was determined in calcium sulfate solutions. The 
solubility of the potash in Dunkirk silt loam was determined in solutions of 
calcium sulfate of various concentrations. 

The solubility of the potash in Dunkirk silt loam in solutions of carbon 
dioxide and calcium bicarbonate was measured. 

The action of various sodium salts in making soil potash soluble was ob- 
served. The solvent action of sodium chloride solutions on different soils 
was measured and the effect of the concentration of the sodium chloride solu- 
tion on the solubility of the soil potash was tested. 

CONCLUSIONS 

1. If commercial acid phosphate has any action in liberating potash in the 
soils used in the experiments, it is due to the gypsum which it contains. 

2. Calcium sulfate in solution does increase the solubility of the potash com- 
pounds in some soils. This action is much more marked on the clay than on 
the silt or sand. This may explain the fact that only some soils are benefited 
by applications of gypsum. Calcium sulfate solutions do not seem to be par- 
ticularly active in dissolving the potash of silt and sands containing mica. 
It is probable that on some, if not all, fertile clay loam and clay soils, some 
potash is made soluble by the application of gypsum. 

3. In the case of Dunkirk clay loam and silt loam, only a small amount of 
calcium sulfate need be present in the solution in order to affect materially 
the solubility of the potash. This may explain why small applications of 
gypsum are quite beneficial on some soils. 

4. The soil potash of Dunkirk silt loam is somewhat more soluble in solu- 
tions of carbon dioxide and calcium bicarbonate than it is in a solution of 
carbonic acid containing the same amount of carbon dioxide. Soils which 
are high in organic matter may derive some soluble potash from the effect of 
the calcium bicarbonate in the soil water after the addition of a large amount 
of lime. 

5. Sodium salts are quite active in dissolving potash from soils. The fact 
that sodium chloride solutions are active in dissolving potash may partially 
explain why beets derive benefit from applications of salt, since beets are very 
resistant to the toxic action of sodium chloride. Wheeler points out that 
beets need sodium for proper growth. These two facts taken together may 
explain the benefits obtained by the use of salt on certain crops. 



256 DONALD KITELEY TRESSLER 



REFERENCES 



(1) Andre, G. 1913 The replacement of potash in certain feldspathic rocks by sub- 

stances used as fertilizers. In Compt. Rend. Acad. Sci. (Paris), t. 57, no. 19, 
p. 856-858. 

(2) Beyer, A. 1871 Concerning the influence of salt solutions and other weathering 

agencies on the decomposition of feldspars. In Jahresber. Agr. Chem., Bd. 13, 
p. 22. 

(3) Bradley, C. E. 1912 The soils of Oregon. Ore. Agr. Exp. Sta. Bui. 112. 

(4) Briggs, L. J., and Breazeale, J. F. 1917 Availability of potash in certain ortho- 

clase-bearing rocks as affected by lime and gypsum. In Jour. Agr. Res., v. 8, no. 
1, p. 21-28. 

(5) Cameron, F. K., and Fallyer, J. H. 1913 The determination of small amounts of 

potassium in aqueous solutions. In Jour. Amer. Chem. Soc, v. 25, p. 1063. 

(6) Curry, B. E., and Smith, T. O. 1914 Granitic soil potassium and its relation to the 

production of hay. N. H. Agr. Exp. Sta. Bui. 170. 

(7) Dietrich, T. 1858 Experiments on the action of different agents on soils and a few 

rocks. In Hoffmann's Jahresber., Bd. 1, p. 29. 

(8) Dietrich, T. 1862 Concerning the action of salt solutions on some rocks and soils. 

In Hoffman's Jahresber., Bd. 14, p. 14. 

(9) Eichhorn, H. 1858 Concerning the action of salt solutions on soils. In Landw. 

Centbl. Deutschl., 1858, pt. 2, p. 169. 

(10) Gaither, E. W. 1910 The effect of lime upon the solubility of the soil constituents. 

In Jour. Indus. Engin. Chem., v. 2, no. 7, p. 315. 

(11) Hall, A. D. 1905 The Book of the Rothamsted Experiments, p. 119. New York. 

(12) Hall, A. D. 1909 Fertilizers and Manures, p. 168, 171, 258. New York. 

(13) Halligan, J. 1911 Soil Fertility and Fertilizers, p. 238. Easton, Pa. 

(14) Hartwell, B. L., and Wessels, P. 1899 The effect of sodium manuring on the 

composition of plants. R. I. Agr. Exp. Sta. Bui. 153, p. 89-119. 

(15) Hilgard, E. W. 1906 Soils, their Formation, Properties, Composition and Rela- 

tions to Climate and Plant Growth, p. 467. New York. 

(16) Iaktjshkin, I. V. 1913 On the action of sodium salts in vegetation experiments. 

In Izv. Moskov. Selsk. Khoz. Inst. (Am. Inst. Agron. Moscou), v. 19, no. 2, 
p. 315-337. 

(17) Lyon, T. L., and Bizzell, J. A. 1918 Lysimeter experiments. N. Y. (Cornell) 

Agr. Exp. Sta. Mem. 12. 

(18) Shaw, G. W. 1905 Field observations on the tolerance of the sugar beet for alkali. 

Cal. Agr. Exp. Sta. Bui. 169. 

(19) Snyder, H. 1893 Soils: The composition of native and cultivated soils and the ef. 

fects of continuous cultivation upon their fertility. Minn. Agr. Exp. Sta. Bul- 
30. 

(20) Soderbaum, H. G. 1911 The fertilizing action of sodium chloride. In Meddel. 

Centralanst. Forsoksv. Jordbrukssomradet, no. 51, p. 12. 

(21) Storer, F. H. 1887 Agriculture in some of its relations to chemistry, v. 2, p. 161, 

New York. 

(22) Way, J. T. 1850 On the power of soils to absorb manure. In Jour. Roy. Agr. Soc. 

England, v. 11, p. 313-379. 

(23) Wheeler, H. J. 1913 Manures and Fertilizers, p. 350, New York. 

(24) Wheeler, H. J. 1905 Plant peculiarities as shown by the influence of sodium salts. 

R. I. Agr. Expt. Sta. Bui. 104. 

(25) Wheeler, H. J., and Adams, G. E. 1905 Concerning the agricultural value of 

sodium salts. R. I. Agr. Exp. Sta. Bui. 106. 



SOLUBILITY OF SOIL POTASH IN SALT SOLUTIONS 257 

(26) Wheeler, H. J., and Tillinghast, J. A. 1897 On the substitution of soda for and 

its value in connection with potash. In R. I. Agr. Exp. Sta. 10th Ann. Rpt., p. 
226-240. 

(27) Wheeler, H. J., and Tillinghast, J. A. 1898 The* fifth year's observations on the 

substitution of soda for and its value in connection with potash. In R.I. Agr. 
Exp. Sta. 11th Ann. Rpt., p. 137-143. 

(28) Wheeler, H. J., Towar, J. D., and Tucker, G. M. 1894 On the substitution of 

soda for and its value in connection with potash. In R. I. Agr. Exp. Sta. 7th 
Ann. Rpt., p. 168-182. 

(29) Wheeler, H. J., and Tucker, G. M. 1895 On the substitution of soda for and its 

value in connection with potash. In R. I. Agr. Exp. Sta. 8th Ann. Rpt., p. 
215-231. 



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